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Complex Chemical Equation Balancing

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Complex Chemical Equation Balancing

Balance each equation using the smallest whole-number coefficients. Do not change subscripts. Show working where space is provided.

Conservation of Mass

1.Which statement best describes atom counts in a balanced chemical equation?

Atoms may disappear if a gas is produced.
Each element has the same number of atoms in the reactants and products.
Only the total number of molecules must match.
Coefficients change one element into another.

2.Complete the statement: In a chemical reaction, matter is not or ; the total mass of the equals the total mass of the .

3.For the equation C₃H₈ + O₂ → CO₂ + H₂O, write the reactant formulae and the product formulae.

Balance Equations

Write coefficients in the spaces. Leave a coefficient as 1 when needed.

4.Balance: H₂ + Cl₂ → HCl

5.Balance the complete combustion of propane: C₃H₈ + O₂ → CO₂ + H₂O

6.Balance: Fe + O₂ → Fe₂O₃

7.Balance: Mg(OH)₂ + HCl → MgCl₂ + H₂O

8.Balance the combustion equation for butane: C₄H₁₀ + O₂ → CO₂ + H₂O. Use the smallest whole-number coefficients.

Count and Check

9.For 2C₃H₈ + 10O₂ → 6CO₂ + 8H₂O, state the number of carbon, hydrogen and oxygen atoms on each side.

10.Choose the correctly balanced equation for iron reacting with chlorine.

2Fe + 3Cl₂ → 2FeCl₃
Fe + Cl₂ → FeCl₃
3Fe + 2Cl₂ → 2FeCl₃
2Fe + 2Cl₂ → 2FeCl₃

More Complex Reactions

11.Balance: NH₃ + O₂ → NO + H₂O

12.Balance the decomposition reaction: NaClO₃ → NaCl + O₂

13.Balance the complete combustion of ethane: C₂H₆ + O₂ → CO₂ + H₂O

14.Select every useful practice when balancing an equation.

Treat an unchanged polyatomic ion as a unit on both sides.
Start with an element found in only one formula on each side.
Change a formula subscript whenever atom counts do not match.
Count atoms on both sides to check the result.
Often leave hydrogen and oxygen until later.

Equations in Context

15.Match each reaction with its application.

2H₂ + O₂ → 2H₂O
2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
2NaCl → 2Na + Cl₂

Formation of water from hydrogen and oxygen
Combustion of petrol-range fuel
Photosynthesis
Electrolysis of sodium chloride

16.Give one reason accurate balanced equations matter when planning chemical production in industry.

Challenge

17.Balance the reaction between calcium nitrate and sodium phosphate: Ca(NO₃)₂ + Na₃PO₄ → Ca₃(PO₄)₂ + NaNO₃

18.Write a concise sequence of steps for balancing a chemical equation, including how you check your final coefficients.

19.Balance the combustion of ethene: C₂H₄ + O₂ → CO₂ + H₂O. If you first choose 1 for C₂H₄, explain why no fractional coefficient appears in this equation.